Sample Size Determination for a Three-Arm Equivalence Trial of Poisson Distributed Responses

• Activity Number: 500
• Type: Contributed
• Date/Time: Wednesday, August 6, 2014 : 10:30 AM to 12:20 PM
• Sponsor: Biopharmaceutical Section
• Author(s): Victoria Chang*+ and Yi Tsong and Zhigen Zhao
• Companies: and FDA and Temple University
• Keywords: equivalence test ; superiority ; ththree-arm clinical trial ; Poisson regression ; sample size ; power

Abstract

The equivalence assessment is often conducted through a three-arm clinical trial and it usually consists of three tests. The first two tests are to demonstrate the superiority of the test and the reference treatment to placebo, and they are followed by the equivalence assessment between the test and the reference treatment. When assay sensitivity has been well established, the equivalence assessment can be reduced to one superiority test of the test treatment over placebo and one equivalence test. In this paper, the author suggested applying the mean incidence ratio to evaluate both superiority and equivalence in order to claim the equivalence between the test treatment and the reference treatment. In addition, the dispersion parameter was introduced to count for overdispersion problem, a very common phenomenon with Poisson therapeutic endpoint. The authors also derived test statistics, power function and gave several power comparison discussions under different conditions.